T-X: The Reveal

On 20th March, the USAF published the requirements for the Advanced Pilot Training Family of Systems (APT FoS) - aka T-X - to replace the ageing T-38. MS&T’s Dim Jones assesses the impact of key performance characteristics.

These were released some 10 months earlier than is usual in the acquisition process and, according to the authors, identified three key performance characteristics: aircraft sustained G; simulator visual acuity and performance; and sustainability. The specific requirements matrix is not presented in a particularly logical order, but the individual criteria seem clear enough. The covering Federal Business Opportunities FBO Notice emphasises that ‘This is not an opportunity for industry to request changes to the APT FoS requirements, but rather to ensure that industry has a clear understanding of the requirements. The rationale is provided to help industry better understand the requirements. The APT FoS Program Office is not soliciting comments on the rationale, and any comments/questions regarding the rationale will be discarded.’ The associated documents do, however, include a mechanism for industry to clarify, ask questions about, or comment on the requirements. In other words, ‘This is the score; now get on with it’.

Taking the key performance characteristics in reverse order, the sustainability requirements embrace Operational and Materiel Availability for aircraft and Operational Availability for the Ground-Based Training System (GBTS), and Materiel Reliability, MTBF, Break Rates and Fix Rates for the aircraft. Compliance with these criteria is well out of my sphere of competence, and all contenders are likely to be able to comply with them, so I will refrain from further comment. Similarly, the requirement for the GBTS are clearly laid out but it is likely that the designs of simulators and other GBTS elements are not yet set in concrete, have been put on hold pending publication of these requirements, and can be adapted to meet them.

We have been exhorted throughout the process to consider T-X as a Family of Systems, and ‘not just about the platform’; however, it is the aircraft performance requirements which will have the most significant impact on the competition as it currently stands. While Sustained G is quoted as being the key characteristic, it is only one of several performance-related targets, although it may be the one which presents the most difficulty. Specifically, the critical requirements are for: a sustained G threshold of 6.5G under specified conditions, with a development objective of 7.5G; an instantaneous G minimum of 8G, with an onset rate of 6G/sec; a sustained turn rate of not less than 12.5o/sec with a turn radius of not greater than 4500ft; an instantaneous turn rate of not less than 18o/sec with a turn radius no greater than 3000ft; and an AOA threshold of 20o, with a development objective of 25o. There is no supersonic flight requirement, nor - contrary to the impression given by Commander AETC as late as November 2014 - any other speed criterion; the aircraft is to be adaptable for boom refuelling, and the simulator equipped to replicate it.

At the outset, the three contenders were all offering platforms based on existing designs: the Alenia Aermacchi M-346/T100; the Korean Aircraft Industries/Lockheed Martin T-50; and the BAE Systems Hawk Advanced Jet Trainer (AJT). Subsequently, Boeing, now in partnership with Saab, announced the development of a new aircraft, Textron AirLand cast their hat in the ring with a proposed development of the Scorpion Light Attack and ISR aircraft and, latterly, Northrop Grumman re-entered the fray, also with a clean-sheet design which, they now reveal, they have been working on for the past two years.

Of the original competitors in their current forms, it is likely that only the T-50 would be able to meet all the threshold, let alone the development, objectives. Hawk AJT would certainly have struggled with the sustained G, AOA and turn radius and, with no fly-by-wire G-limiting, probably with the G-onset as well. M-346 with a high thrust-to-weight ratio and fly-by-wire, should be able to cope with everything but, possibly, the sustained-G requirement. It is self-evident that any new aircraft will be designed to meet all the requirements, and unlikely that any of these constraints have come as a complete surprise to the competing partnerships; indeed, in a progressive change of strategy, Northrop Grumman who were originally the manufacturing partner for the Hawk AJT, have also assumed prime responsibility within the partnership, which will now offer their new design and take advantage of the extensive work completed by BAE Systems on other aspects of the requirement, such as the air training system, including embedded avionics, and L-3’s work on ground training systems. There has been no formal announcement of the withdrawal of Hawk AJT from the competition, rather an assumption by inference.

The slide to the right of the projected in-service date (now 2023), necessitated by budget constraints and in spite of the increasing cost of keeping T-38 in the air, has definitely played into the hands of the clean-sheet designers, although the level of investment during a period of defence industry downturn must have required some brave decisions. More cynical observers of previous trans-Atlantic aircraft procurement competitions than I might suggest that there has been some fairly effective lobbying in Washington to load the dice in favour of, if not to ensure, a US-bred solution. However, who can wonder at that? This is, after all, by far the biggest trainer contract of all time, the customer is the USAF, and the overseas competitors will doubtless have entered the fray with their eyes open.

The Program Office intends to host a Pre-Solicitation Conference in mid-April, to discuss industry’s responses. In the longer term, we await the unveiling of the Boeing, Northrop Grumman and Textron AirLand designs with keen anticipation.